The Research Of VOCs Components Characteristic In A Parking Area

Urban atmospheric volatile organic compounds(VOCs)is an important precursor of secondary organic aerosol(SOA).SOA is an important component of fine particles,while it largely contributs to atmospheric fine particles PM2.5 in uban air.Vehicle emission is the main source of VOCs in the ambient air of urban areas.Shopping mall parking ramps are a densely packed areas,in which the level of VOCs are very high due to incomplete combustion and evaporation from fuel tanks.This urban area has not caught enough attention as a hazardous pollution source.In this research,we collected air samples via SUMMA canisters or Tedlar air bags and sampled them by GC/MSD method in a laboratory environment in order to realize the qualitative and quantitative analysis of 107 kinds of VOCs present in the car park.We detected the VOCs in a confined shopping mall parking ramp,one arterial road,university campus air,and vapor gasoline phase of gas tanks in Dalian by this method.Analysis results show that:(1)There is different emission of TVOC(total volatile organic compounds)with different vehicle engine sizing or engine displacement in idling condition.Emission of 1.5L small-displacement vehicles is up to 148.8mg/m3,which is 7.45～117 times of other types vehicles tested in this study.The amount of TVOC emissions gradually decreased as the engine displacement increased.The alkane compounds concentration percentage was the highest in gasoline cars and diesel cars.(2)The vapour gasoline components of octane rating No.92 and No.94 fuels are similar.The concentration of alkane compounds is up to 63%～65%,halogenated hydrocarbons just 0.42%～0.47%.The amount of halogenated hydrocarbons is very small in the gasoline vapor phase.(3)The TVOC concentration of a shopping mall parking area one level below ground,two levels below ground,the arterial roadside environment,and the campus air is:two levels below ground parking area>one level below ground>the roadside environments>the campus air.The mass concentration of TVOC in the parking area is 2.89～21.20 times of roadside environments,2.13～19.71 times of the campus air.(4)The TVOC mass concentration of the two levels below ground parking area was significantly increased during the weekend and holiday,but with the holiday ending,the TVOC concentration gradually returned to normal levels.(5)In the sampling sites mainly influenced by vehicle exhausts,the benzene/toluene ratio is closer to the benzene/toluene ratio(0.25)of plain tested gasoline vapor phase.There was a significant correlation(R2=0.7)between the concentration of roadside and parking area aromatic compounds,which indicates that the same source of aromatic hydrocarbon compounds is present in roadside and parking areas.(6)The discharge of alkane compounds,alkenes,and aromatic hydrocarbons into outside environment was 9.20g/h,2.61g/h,9.15g/h,respectively.(7)We assessed the health risk of benzene,toluene,ethylbenzene,p-xylene,o-xylene,and styrene in the parking ramp.By calculating the HI>1 of benzene and tolune this indicated that the concentration of BETX can increase the non-carcinogenic health risks in parking areas.Benzene lifetime carcinogenic risk is higher,which means potential carcinogenic risk to worker and pedestrian health.